The major emphasis of the total program is on the chemistry and metabolism of sterols and sphingolipids, two classes of compounds generally considered unique to the cell structure and function of eukaryotic organisms. The program includes 6 major categories. Project area I concerns sterol intermediates in the biosynthesis of cholesterol and includes detailed metabolic, enzymatic and mechanistic studies of the conversion of 14Alpha-methyl-, 14Alpha-hydroxymethyl-, and 14Alpha-formyl-substituted sterols to cholesterol and to intermediates in the biosynthesis of cholesterol; exploration of the possible role of 14Alpha-formoyloxy-substituted sterols as potential intermediates in the enzymatic removal of carbon atom C-32 of sterol precursors of cholesterol; and determination of the chemical nature of sterols of mouse LM fibroblasts; and studies of the mechanisms involved in the enzymatic conversion of Delta8(14)-sterols to cholesterol. Project area II includes: studies of the possible role of 14Alpha-hydroxymethyl- and 14Alpha-formyl-substituted sterols as regulators of sterol synthesis in cultured mammalian cells; studies of the role of oxygenated derivatives of cholesterol in the regulation of the biosynthesis of cholesterol including investigations of the occurrence and chemical nature of oxygenated sterols in: (a), low density lipoproteins of human plasma, and (b), commercial preparations of egg yolk and butter; and studies directed towards the purification of 3-hydroxy-3-methylglutaryl-coenzyme A reductase from liver microsomes of normal rats. Project area III involves a number of studies of the effects of selected oxygenated sterols on developmental processes in insects. Project area IV involves studies of the chemistry and biosynthesis of phytosphingosine, and the possible coordination of the synthesis of sterols and of sphingolipids in cultured mammalian cells. Project area V involves stereochemical and mechanistic studies involved in the area of lipid metabolism. Project area VI involves general and specific applications of mass spectrometry and nuclear magnetic resonance spectroscopy to sterols, sphingolipids, and biochemical problems.